| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 14°F | 34°F | 24°F | 2.7" |
| February | 14°F | 36°F | 25°F | 2.8" |
| March | 23°F | 45°F | 33°F | 3.3" |
| April | 34°F | 60°F | 47°F | 3.5" |
| May | 45°F | 71°F | 57°F | 3.4" |
| June | 54°F | 78°F | 66°F | 5.5" |
| July | 60°F | 84°F | 71°F | 4.1" |
| August | 57°F | 81°F | 69°F | 4.3" |
| September | 50°F | 75°F | 62°F | 4.1" |
| October | 40°F | 62°F | 50°F | 6.2" |
| November | 29°F | 50°F | 39°F | 3.0" |
| December | 21°F | 40°F | 30°F | 4.2" |
| Index | Petersham | Massachusetts | National |
| Air quality index | 40 | 40 | 42 |
| Pollution index | 7,859,360 | 8,399,610 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 312 |
| Days with moderate air quality | 52 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.030% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.030% |
| Lead | 0.320% |
| Mercury | 0.070% |
| City | Population | Air Quality Index | National Avg. |
| Winchendon, MA | 4,673 | 34 | 32.0% |
| Athol, MA | 8,323 | 34 | 32.0% |
| Orange, MA | 3,882 | 34 | 32.0% |
| Baldwinville, MA | 2,137 | 34 | 32.0% |
| Gardner, MA | 20,605 | 40 | 20.0% |
| Petersham, MA | 256 | 40 | 20.0% |
| City | Population | Air Quality Index | National Avg. |
| Yankee Hill, CA | 256 | 46 | 8.0% |
| Peetz, CO | 256 | 19 | 62.0% |
| Pulaski, GA | 256 | 39 | 22.0% |
| Decker, IN | 256 | 36 | 28.0% |
| Hickory, KY | 256 | 44 | 12.0% |
| Petersham, MA | 256 | 40 | 20.0% |
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